Wednesday 29 February 2012

The bite of T. rex.

One of the debates that surfaces regularly in dinosaur science is how hard could Tyranosaurus rex (favorite dinosaur of small boys everywhere) actually bite. This has implications for the behavior of the living animal, as if it had a hard bite it would have been one of the most formidable predators ever, but if it had a week bite it was probably a scavenger. A similar debate runs with regard to T. rex's running speed; fast equals formidable predator, slow equals scavenger.

In a paper published in the journal Biology Letters on 29 February 2012, Karl Bates of the Department of Musculoskeletal Biology at the University of Liverpool and Peter Falkingham of the School of Earth, Atmospheric and Environmental Science at the University of Manchester, present a new computer simulation of the biting power of adult and juvenile T. rex's, based upon computer models calibrated by testing the computer estimates of the biting power of Human volunteers and Mississippi Crocodiles against the results obtained experimentally.

Three dimensional computer models of T. rex. (a) With soft tissue reconstructed (red, adductor mandibulae externus group; blue, adductor mandibulae posterior group; purple, pterygoideus group). (b) Model with joint centres (green circle), muscles (red cylinders), and ‘contact’ springs (blue spheres and cylinder) on the teeth in the initial simulation starting pose. (c) Model during sustained biting. Bates & Falkingham (2012).

Bates & Falkingham compared the calculated bite of juvenile and adult T. rex specimens to the known biting power of Humans and Mississippi Crocodiles and the calculated biting power of the Jurassic Therapod Allosaurus and concluded that the bite of the adult T. rex was considerably grater than would have been predicted from studying the juvenile, and consistent with the possibility that T. rex might have had the hardest bite of any terrestrial animal ever. They also compared the study to previous studies on T. rex and other large Theropods.
Comparison of the biting forces obtained from this study (white) with that obtained from earlier studies. A. Adult. J. Juvenile. Bates & Falkingham (2012).

One animal that seems to be notably absent from this study, and which in the past has been considered a contender for the hardest bite ever is the Cretaceous Giant Crocodile Sarcosuchus. In modern environments Crocodiles generally bite harder than mammals, so comparing T. rex to smaller crocodilians (the Mississippi Alligator is not even the largest extant crocodilian), smaller theropods, primates and a big cat (cats kill by squeezing the neck quite gently; the more tear-the-throat-out approach of Hyenas produces a far harder bite), does give T. rex a bit of an advantage in a hardest biter competition.

A second star in the T Chamaeleontis system.

T Chamaeleontis is a young star (about 7 million years old) roughly 326 light years from Earth in the constellation of Chamaeleon. It has a mass of about 1.5 × that of our sun, and is surrounded by an accretionary disk; a disk of dust and gas from which planets can potentially form. In February 2011 a team of scientists lead by Nuria Huélamo, of the Centro de Astrobiología at European Space Astronomy Centre Campus in Madrid, announced the discovery of a planet orbiting T Chamaeleontis at a distance of 6.7 AU (6.7 times as far from the star as the Earth is from the Sun, or slightly greater than the distance at which Jupiter orbits), within a gap in the disk surrounding the star, in a paper in the journal Astronomy & Astrophysics.

Simulation of a journey through the T Chamaeleontis System.

In a paper published on the online arXiv database at Cornell University Library on 1 February 2012, a team of scientists lead by Joel Kastner of the Center for Imaging Science and Laboratory for Multiwavelength Astrophysics at the Rochester Institute of Technology, describe a new study of the T Chamaeleontis system, made from the Australian National University’s Siding Spring Observatory in New South Wales, from which they conclude that the neighboring star 2M1155–79 is in fact a part of the T Chamaeleontis system.

2M1155–79 is a young (about ten million years old) Red Dwarf star with a mass 30% of that of the Sun, and an effective temperature of 3400 K (compared to 5770 K for our sun). It is separated from T Chamaeleontis by a distance of about 38 kAU (38 000 times as far from T Chamaeleontis as the Earth is from the sun).

This may at first seem a little far out to be part of the same system, but on the scales at which star distances are measured is not that far. The Earth is 50 light seconds from the Sun, giving a separation between 2M1155–79 and T Chamaeleontis of 1 900 000 light seconds, or 22 light days. The nearest star to our Sun, the Red Dwarf Proxima Centauri, is 4.2 light years away, so 2M1155–79 is 70 times as close to T Chamaeleontis as Proxima Centauri is to the Sun.

Kastner et al. propose that 2M1155–79 will take a million years to orbit T Chamaeleontis, and suggest that it be renamed T Chamaeleontis B (with T Chamaeleontis becoming T Chamaeleontis A). Furthermore they note that binary partners for very young stars seem to be far more common than for the general population of stars, and that the presence of these stars, and their gravity, must have a profound effect on the formation of planets.

An artists impression of the T Chamaeleontis system. European Southern Observatory.

Tuesday 28 February 2012

What Hayabusa brought back from 25143 (Itokawa).

In November 2005, the Japan Space Agency's probe Hayabusa touched down on the near Earth asteroid 25143 (Itokawa) in order to collect samples. The probe landed in the Muses Sea are of the asteroid, and was due to fire a projectile into the surface in order to dislodge material from the surface for collection. In the event this projectile did not fire, but the probe was able to collect a small number of mineral grains floating above the surface, of the asteroid, which has negligible gravity. This material was returned to Earth for analysis in June 2010.

Close up image of taken from Hayabusa. A & B indicate possible recent impact sites. Circles represent possible hydrological sinks. Arrows point to areas of talus (rubble). Curved lines indicate possible debris flow. Japan Space Agency.

25143 (Itokawa) is a 558 m long, 288 m diameter asteroid with a 556 day period (year) on an orbit that crosses that of the Earth. It is roughly bean-shaped and has a surface covered in rubble; in fact it may be rubble all the way through. The asteroid rotates on its axis every 12 hours, and has a gravity of about a millionth of the Earth's (though this varies from place to place, dependent on the local density of the asteroid). 25143 (Itokawa) has a number of areas on the surface that appear to be hydrological sinks.

These hydrological sinks are surprising in on an asteroid, which is not somewhere we would expect to find water, but are attributed to the former presence of ice. It is thought that the asteroid may have formed further out in the solar system, where chunks of ice (not necessarily water ice) were incorporated into its makeup. At some point it was shifted onto its current orbit, where it passes closer to the sun. This caused the asteroid to heat up, and the ice to sublimate (turn directly from a solid to a gas) in a similar way to material evaporating from the surface of a comet. After this happened the loose rocky material covering the new void subsided forming a sinkhole.

The orbit of 25143 (Itokawa). Bellatrix Astronomical Observatory.

On 27 February 2012 a paper was published in the Proceedings of the National Academy of Sciences, by a group of scientists lead by Eizo Nakamura of the The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry at the Institute for Study of the Earth’s Interior at Okayama University, detailing the results of a study of five mineral grains brought back from 25143 (Itokawa) by Hayabusa, and the deductions made from these studies.

The grains were made of the minerals olivine, pyroxene, diopside and plagioclase, all common in igneous rocks from the Earth and the Moon, with small inclusions of other common minerals. They ranged in size from 30 × 40 μm to 90× 110 μm, and all were covered in tiny pits, apparently impact craters caused by the action of tiny grains 10-20 nm across. This is interesting as these may not have originated from 25143 (Itokawa), or a similar asteroid. In the Solar System objects larger than 5 μm tend to fall towards the sun, whereas those smaller tend to be carried outwards by the solar winds.

Scanning Electron Microscope images of an olivine grain from 25143 (Itokawa). (A) Detail of part of the grain as shown in inset. F1, F2 & F3 represent fracture plains (the plains along which a mineral will split). C, D & E are areas of magnification. (B) Back Scattered Electron Microscope image of (A) showing mineral textures; Ol is olivine, Pl is plagioclase. (C, D & E) Detail of (A) showing craters made by tiny impacts. These are 100-200 nm across, implying impactors 10-20 nm across. From Nakamura et al. (2012).

While the minerals from which 25143 (Itokawa) are made are not unusual they do tell us something about the history of the asteroid. The minerals present would generally form at a temperature of about 900°C, far hotter than the temperature likely to be reached during the formation of a 300 m radius asteroid. From this Nakamura et al. conclude that 25143 (Itokawa) was formed as part of a larger body, from which it has become separated at some point.

The origin of the cthonian planets orbiting KIC 05807616.

In December 2011 a team lead by Stephane Charpinet of the Institut de Recherche en Astrophysique et Planétologie, Université de Toulouse publish a paper in the journal Nature detailing the discovery of a pair of cthonian planets orbiting the B-type subdwarf star KIC 05807616. A B-type subdwarf star is a very hot small star fusing helium; these are thought to be the result of a Red Giant star (a star that has used up all its hydrogen then begun to fuse helium, consequently causing its outer layers to expand massively due to the additional heat) having somehow lost its outer layers, usually as a result of interaction with a smaller binary companion. Cthonian planets are planets that have been absorbed by the expansion of a star at the end of its hydrogen-fusing life, then re-emerged when the outer layers were shed for some reason (until 2011 an entirely theoretical class of planet.

Model of the origin of the KIC 0580761 system. Charpinet et al. (2011).

However this model leaves several unanswered questions about the origin of the KIC 0580761 system. Firstly KIC 0580761 lacks a binary companion which could have stripped the outer layers from the primary star. Charpinet et al. attributed this to the interaction of the planets with the star, but it is unclear how this could happen. Secondly the two planets are locked in a 3:2 tidal resonance (i.e. one orbits the star twice in the time the other does three times, planets in such orbits 'lock' into a resonance due to tidal effects). It is hard to see how this resonance could have survived while the planets were within the star, which would have exerted a severe braking effect on the planets.

In a paper published on the online arXiv database at Cornell University Library on 6 February 2012, Ealeal Bear and Noam Soker of the Department of Physics at the Israel Institute of Technology suggest an alternate model for the origin of the KIC 0580761 system, in which the star lost its outer layers when its expansion brought it into contact with a massive Gas Giant type planet, that was ripped apart in the process. Under this scenario the two planets originated in this massive interaction, being fragments of the core of the massive planet (there may have been others). The violent reaction between the planet and the star caused the loss of both the outer layers of the Red Giant, and the dense atmosphere of the planet.

Bear and Soker also note that the inner of the two planets appears to be evaporating due to the proximity of the ultra-hot star.

Sunday 26 February 2012

Earthquake shakes south Taiwan.

Slightly before 10.35 am local time (slightly before 2.35 am GMT) on Sunday 26 December 2012, an Earthquake measured as 5.9 on the Richter Scale at a depth of 22.4 km by the United States Geological Survey struck a mountainous region of southern Taiwan, causing shaking that was felt across much of the island. The shaking was apparently particularly severe in the southern city of Kaohsiung, where it caused buildings to sway severely for about 7 seconds, leading to widespread panic, though their does not appear to have been any significant damage or casualties.

Map of southern Taiwan, showing the epicenter of the quake, and the areas most severely shaken. United States Geological Survey.

Taiwan lies on the borders of two tectonic plates, the Philippine Sea Plate and the Eurasian Plate. The relationship between the two is quite complex, with the Eurasian plate being subducted under the Philippine Sea Plate in the south of the island, and along the Luzon trench, which extends south from the island to the Philippines, and the Philippine Sea Plate being subducted under the Eurasian Plate in the north of the Island, and along the Ryuku Trench which extends northeast from the island to Japan.

This leads to a large number of quakes on the island, though most do not do serious damage. The worst quake in recent times was in 1999, when an Earthquake in the center of the island killed over 2300 people.

Planetary formation around GM Cephie.

GM Cephei is a young (about four million years old) variable star in the Elephant's Trunk Nebula (Trumpler 37), about 2450 light years from Earth; the name GM Cepei means 195th variable star in the constellation of Cepheus. CM Cephei has an estimated mass of 2.1 times that of our sun, and a volume between 100 and 900 times as great (this is not unusual in a star still collapsing under its own weight, which is how stars form). It is classified as a Type II T Tauri irregular variable star, a young star with a variable output due to patchy heat distribution and material still accreting onto its surface.

The Elephants Trunk Nebula (Trumpler 37). Image from NASA's Spitzer Space Telescope.

In a paper published on the arXiv online database at Cornell University Library on 23 February 2012, and due to be printed in a forthcoming edition of the Astronomical Society of the Pacific Conference Series, a team of scientists led by Chia-Ling Hu, of the Institute of Astronomy at the National Central University of Taiwan and the Taipei Astronomical Museum, describe the discovery of a regular pattern in the variability of GM Cephie, and the conclusions drawn from it. The discovery was made from results obtained by the Lulin Observatory in Taiwan and the Tenagra Observatory in Arizona, which were studying the system as part of the international Young Exoplanet Transit Initiative (YETI), which is concentrating on the stellar nurseries of Trumpler 37 and 25 Ori.

The YETI team observed that GM Cephie dimmed every 311 day for a period of 39 days, and that it turned slightly bluish as it did so. They theorize that this dimming is caused by a cloud of material orbiting the star at a distance of 1.16 AU, with a volume in excess of 4 million times that of our sun. They calculate this cloud of material would contain about 2.269 × 10¹⁸ kg (that's 2 269 000 000 000 000 000 kg) of silica dust, enough for a small-to-medium-sized asteroid.

Earthquake in Tuva Republic, southwest Siberia.

Slightly after 1.15 pm local time (slightly after 6.15 am GMT) on Sunday 26 February 2012, the Tuva Republic in southwest Siberia was hit by an Earthquake measured by the United States Geological Survey as measuring 6.7 on the Richter Scale, and occurring at a depth of 11.7 km. The quake was centered between the villages of Karaus and Kara Khem, but was felt across much of Siberia and neighboring Mongolia. There are no reports of any serious damage or casualties, but they would not be surprising for an Earthquake of this size, even in a remote region. The quake did apparently cause a localized blackout.

The location of the Tuva quake. United States Geological Survey.

Earthquakes in Central Asia are generally attributed to the movement of India, which is pushing into Eurasia from the south, causing the folding and uplift that creates the mountains of the Himalayas, the Tibetan Plateaux, and Siberia.

The Sayan Mountains of the Tuva Republic, a result of uplift caused by the impact of India into Eurasia.

Saturday 25 February 2012

New species of Bat discovered in Vietnam.

Bats are the second largest group of mammals, with about 1240 known extant species; 20% of all named mammal species are bats. They are at their most diverse in the tropics, and tend to be small, which makes it likely that there are many more species yet to be discovered, though it is also likely that many of these unnamed bats may be at risk due to habitat loss.

In a paper in the February edition of the Journal of Mammalogy a team of scientists lead by Vu Dinh Thong of the Institute of Ecology and Biological Resources in Hanoi describe the discovery of a new species of Leaf-nosed Bat from Vietnam.

The new species has been named as Hipposideros griffini, or Griffin's Leaf-nosed bat (in Vietnamese Dơi nếp mũi Grip-phin) in honour of the late Donald Redfield Griffin of Rockefeller University in New York, a noted bat researcher.

Griffin's Leaf-nosed Bat, Hipposideros griffini. Thong et al. (2012).

The new bat is not described from newly discovered populations, but rather from populations formerly attributed to another species, Hipposideros armiger (Armiger's Leaf-nosed bat), which it closely resembles, although H. griffini is somewhat smaller, and has a distinct call. DNA analysis confirmed that it was a distinct species, separate from H. armiger and other species of Leaf-nosed Bat.

H. griffini was found at a number of locations, including both primary rainforest, disturbed/secondary rainforest, mountains, karst (eroded limestone terrain), and on an off-shore island, Cat Ba in Ha Long Bay. As such the species seems highly adaptable, and not in any immediate threat due to human activity. Thong et al. suggest that the species is likely to be found in Cambodia, China, Lao People’s Democratic Republic, Myanmar and Thailand as well as in Vietnam, although they are unable to confirm this without further research.

Metal sphere falls on Anapurus, northeast Brazil.

At 6.00 am local time on Wednesday 22 February 2012, the town of Anapurus, in Maranhão State, northeast Brazil was hit by a metal sphere, roughly 1 m across and weighing about 30 kg, which reportedly crashed into a stand of cashew trees, before coming to rest in a garden.

Residents of Anapurus inspect the metal sphere. Folha News (2012).

The metal sphere attracted a large number of visitors to the area, before being taken into custardy by the local Military Police. From here the object was brought to the attention of Gustavo Rojas of the Grupo de Astronomia at Federal University of Sao Carlos, who identified it as probably being a part of an Ariane 4 rocket, used by the European Space Agency until 2003.

Spacecraft tend to contain a lot of thick-walled spherical tanks, which is the most stable shape for a tank containing liquids under pressure in a changing gravity field. Unfortunately this is also a good shape for surviving re-entry into the Earth's atmosphere, so as the amount of space junk orbiting the Earth increases, so does the number of metal spheres falling from the sky. As yet there have been no reported cases of death or serious injury caused by space junk, but it does seem to be an increasing hazard on Earth as well as in orbit, with several reports of damage to property now coming in each year.

Image showing each of the 19 000 man-made items larger than 10 cm in Earth's orbit, as of July 2009. NASA/Orbital Debris Program Office.

Eruptions on Mount Turrialba

On 11 January 2012 people living close to Mount Turrialba in central Costa Rica reported hearing rumbling from the mountain, according to the Observatorio Vulcanológico y Sismológico de Costa Rica-Universidad Nacional. The next day there was a small eruption from a new vent on the southeast flank of the west crater, with an ash cloud rising 500 m into the atmosphere above the volcano, and the Turrialba Volcano National Park, which surrounds the volcano was closed as a precaution, and surrounding communities were out on a state of high alert. The ash cloud eventually reached a height of 4 km. Residents in the area reported seeing a dark plume from the fissure (probably a mixture of gas, steam and ash) accompanied by a white plume from the central crater (probably steam), and ash-fall was recorded in the town of Tres Rios, 27 km to the southwest of the volcano.

Archive photo of Mount Turrialba. From Monumental FM (Costa Rican radio station).

On 18 January scientists from Observatorio Vulcanológico y Sismológico recorded gas emissions, reddish flames and tephra (rocks and/or ash) being ejected from the new vent, an ash cloud over the volcano reached 6.1 km, and ash-fall was recorded in La Central, 4 km to the southwest. The scientists again visited the volcano on the 2nd and third of February, and reported incandescence (glowing) and temperatures of 600-700°C from the vent, and two other vents on the crater rim, that had opened in 2010 and 2011 respectively.

Turrialba is a stratovolcano located at the end of a volcanic ridge. It has a complex of three craters at its summit, of which most recent activity has been at the westernmost, the central crater having been inactive since a series of eruptive explosions in the 1860s.

Aerial photo of the summit of Mount Turrialba. Federico Chavarria Kopper (1999)

The volcanoes of Costa Rica, and Central America in general, are fed by the subduction of the Cocos Plate to the southeast beneath the Caribbean Plate, on which Central America sits. The Cocos Plate is subducted in the Middle American Trench, which runs offshore along the coast of Central America. As it sinks into the Earth it is is heated by the heat of the planet's interior and partially melts. Some of the melted material then rises up through the overlying Caribbean Plate as magma, forming the volcanoes of Central America.

In this sense Central America can be seen as an island arc, albeit one that has joined up completely. 50 million years ago the isthmus did not exist at all, and it only completed the join between North and South America about 3 million years ago, allowing the fauna's of North and South America to mix for the first time, and causing a cooling of the global climate as the warm current between the tropical Pacific and the tropical Atlantic was halted.

Friday 24 February 2012

Greenpeace activists occupy drilling ship in New Zealand.

Early on the morning of Friday 24 February 2012 seven activists from the environmental group Greenpeace, including actress Lucy Lawless (better known as Xena the Warrior Princess) boarded the Liberian registered drilling exploration ship Noble Discoverer in the Port of Taranaki 0n North Island, New Zealand, as a protest against plans to search for oil in the Alaskan Arctic on behalf of the oil giant Shell. The ship had been chartered from its owners, Noble Drilling, after Shell was granted a license to prospect for oil in the Chukchi Sea, of the coast of Alaska, by the US Interior Department in August 2011.

Greenpeace activists atop the drilling derek on board the Noble Discoverer. Image from Greenpeace.

Greenpeace objects strongly to oil exploration in the Arctic, where ecosystems are thought to be especially vulnerable to oil spills, and where any major oil spill would be next to impossible to clean up. They point out that the cleanup operation after the blowout on the BP chartered oil rig Deepwater Horizon in the Gulf of Mexico involved over 6000 ships and managed to recover only 17% of the oil spilled. The US Coast Guard has stated that such a cleanup in Arctic waters could not be attempted.

They also point out that Arctic environments are particularly vulnerable to the threat of global warming, and that the best means to protect them would be to cease exploration for new hydrocarbons and switch to alternative forms of energy generation as quickly as possible.

The New Plymouth Police, within whose jurisdiction Taranaki falls, have described the action as illegal, but have agreed to leave the protestors, who reportedly have several days worth of supplies, in place for the time being, stating that safety is their paramount concern. Shell have expressed 'disappointment' at the Greenpeace action, which they say endangers the lives of both the protestors and the crew, and have said they have offered to discuss their plans for drilling in the Arctic with Greenpeace.

This is the second Greenpeace action against Shell this week, on Monday (21 February 2012) protestors scaled the National Gallery in London, where Shell were hosting a reception, and unscaled a 40 m² banner reading "It's No Oil Painting", also in protest against the planned Arctic Drilling.

The location of the Chukchi Sea, where Shell hope to drill for oil. AP.

Elephant trackways from the United Arab Emirates.

Elephants have a long and well understood fossil record, but this can usually only tell us about the physical attributes of Elephants, i.e. their morphology, diet etc. Modern elephants display sophisticated social behavior, with solitary males and herds made up of females and juveniles lead by dominant matriarchs, something hard to detect in the fossil record.

In a paper published in the journal Biology Letters on 22 February 2012, a team of scientists lead by Faysal Bibi of the Institut de Paléoprimatologie et Paléontologie Humaine at the Université de Poitiers describe the discovery of a set of Late Miocene elephant trackways at Mleisa in the United Arab Emirates that apparently show evidence of both large, solitary Elephants and herds including adults and juveniles of various sizes, as is seen in modern Elephants.

Composite aerial photograph of the study site from GigaPan.

The trackways show the tracks of a herd of Elephants extending for 190 m, bisected the track of a single large elephant, which extends for 260 m. The large elephant has a stride length of 3 m, comparable to that of modern African Elephants. The largest member of the pack was apparently of similar size to the solitary Elephant, which is harder to explain. Modern Elephants show sexual dimorphism, and the females are considerably smaller than the males, so if the tracks do represent a herd lead by a female matriarch, then that female must have been similar in size to a male, and considerably larger than modern female Elephants. Bibi et al. suggest that a review of sexual dimorphism in fossil elephants may shed light on this mystery.

There are three modern species of Elephant, divided into two genera; Elephas maximus, the Indian Elephant and the African Elephants Loxodonta africana (African Bush Elephants) and Loxodonta cyclotis (African Forest Elephants). Neither genera was around in the Late Miocene, but the ancestors of the two groups were already separate and matriarchal herding is seen in both groups, suggesting that the behavior should have arisen by then. Three species of Elephant are known to have been present in the area at the time when the tracks were made; Stegotetrabelodon syrticus, Deinotherium sp. and ‘Mastodongrandincisivus. Of these Stegotetrabelodon syrticus is though most likely to have been the track-maker, as it was the most abundant, though it is not possible to be 100% sure that the solitary track-maker and the herd track-makers were of the same species. The genera Elephas and Stegotetrabelodon are more closely related to one another than either is related to Stegotetrabelodon, so even if matriarchal behavior had arisen in the common ancestor of both before the Late Miocene, it does not necessarily mean that the same behavior would have been seen in Stegotetrabelodon.

Reconstruction of the formation of the track site, with Stegotetrabelodon syrticus as the track-maker, by paleoartist Mauricio Antón.

Pleistocene rock carving from Brazil; possibly the oldest art in the Americas.

The earliest people arrived in the Americas some time between 12 000 and 13 500 years ago. They are known from burials and tools scattered (albeit thinly) across both North and South America. Art made by these early Americans is far less well known. A series of linear marks from a cave in Epullán Grande in Argentina were found bellow an archaeological horizon with dated to 11 600 years ago, but whether the marks were man-made is unclear. Some cave paintings at Baixão do Perna in Brazil have been associated with charcoal in the same cave dated to 10 800 years ago, but it is unclear if the charcoal-makers were responsible for, or even contemporary with, the cave paintings. Rock art at a number of sites in the Southwest United States appears to show mammoths, implying they may be of a great age, but none of these has been reliably dated.

In a paper published in the journal PLoS ONE on 22 February 2012, a team of scientists lead by Walter Neves of the Laboratório de Estudos Evolutivos Humanos at the Instituto de Biociências at the Universidade de São Paulo, report the discovery of a humanoid figure carved into a rock surface at the Lapa do Santo rockshelter in Central-Eastern Brazil. The figure has been chipped into the rock and has a 'C' shaped head, three digeted limbs and a large phalus.

The Lapo de Santa rock carving. From Neves et al. (2012).

The chronology of the Lapo de Santa rock shelter is well understood. There appear to have been three distinct phases of settlement there. The first lasted from about 12 000 to about 8000 years ago. The second was about 4400 years ago, and the third about 800 years ago. In all cases the settlers appear to have lived by gathering and hunting small game.

The rock carving was found 30 mm bellow a hearth dated to 9470 years before the present. Mineral grains from immediately above the carving were dated using Optically Stimulated Luminescence, a technique that can date the last time mineral grains were exposed to sunlight, giving an age of at least 10 200 years, and probably closer to 11 700 years.

Thursday 23 February 2012

Possible eruption on Tinakula.

Tinakula is a volcanic island in the Santa Cruz Islands, part of the Solomons, roughly 500 km east of San Cristobel, or 500 km north of Vanuatu. The island forms the peak of a massive stratovolcano (cone shaped volcano) rising 3-4 km from the sea floor to form an island 3.5 km across and 851 m high. The summit crater of Tinakula was breached by a landslide in 1965, forming an open scarp on the west side of the island that runs down to the sea.

Due to its remote location Tinakula is not visited very often, and so is not monitored from the ground. However it is visible to satellites, allowing a level of surveillance. On 13-14 February 2012 NASAs MODIS Instrument detected increased heat coming from Tinakula, and on 14 February the Earth Observing-1 satellite imaged a plume of ash and smoke issuing from the summit of the volcano.

Image of Tinakula captured by the Earth Observing-1 satellite on 14 February. Scale bar is 500 m. Earth Observatory.

Eruptions of this kind do not seem to be unusual on Tinakula. Satellites detected similar activity in 2004, 2006, 2007, 2009, 2010 and 2011. Eruptions were observed by boat in 1984 and 1985, and an eruption in 1971 was observed by airplane and seen from Trevanion Island, 20 km to the south; this eruption caused a small tsunami, though no-one was hurt. Numerous other explosions have been recorded on the island since its discovery by the Spanish in 1595. The island was inhabited till about 1840, when the entire population was wiped out in a particularly violent episode. Since then there have been sporadic attempts to colonize Tinakula by people from neighboring islands, but all have been abandoned.

The Santa Cruz Islands are a volcanic island arc on the boundary between the Pacific and Australian Plates. The Australian Plate is being subducted beneath the Pacific Plate. As it sinks into the Earth's interior it is heated, and partially melts. Some of the melted material rises through the overlying Pacific Plate as magma, forming the volcanoes of the Santa Cruiz Islands, including Tinkula.

Silicate snow on HD 189733b.

HD 189733b was discovered in 2005 by astronomers working at the Haute-Provence Observatory; its discovery was announced in a paper in the journal Astronomy & Astrophysics by a team of researchers lead by François Bouchy of the Laboratoire d'Astrophysique de Marseille and the Haute-Provence Observatory. It is a Hot Jupiter type planet 63 light years from Earth in the constellation of Vulpecula, orbiting a K-type Orange Dwarf star (HD 189733A), with a mass 80% that of the suns, at a distance of 0.03 AU, i.e. 3% of the distance between Earth and the Sun, or one tenth of the distance at which Mercury orbits the Sun.

Illustration of HD 189733b by Martin Kornmesser of the Hubble European Space Agency Information Centre.

HD 189733b is one of the best studied Hot Jupiter type-planets. It has a mass of 1.13 × that of Jupiter, 6.17 × Jupiter's volume. It orbits HD 189733A once every 53.25 hours. The planet has an atmosphere comprised primarily of hydrogen (H₂) and helium (He), but significant amounts of water (H₂O), methane (CH₄) and carbon monoxide (CO) have been also detected.

In a paper published on the online arXiv database at Cornell University Library on 21 February 2012, and accepted for publication in the Monthly Notices of the Royal Astronomical Society, a team of scientists lead by Catherine Huiston of the Astrophysics Group at the School of Physics at Exeter University describe an attempt to produce a vertical temperature profile for the atmosphere of HD 189733b using the Hubble Space Telescope, and the conclusions derived from their results.

Huitson et al. resolved the temperature of HD 189733b to 1280 K in the lower atmosphere, bellow heights of 500 km, rising to 3600 K in the outer layers of the atmosphere. They also found a distinct scattering effect in the atmosphere that they attributed to the presence of magnesium silicate (MgSiO₃).

MgSiO₃ is of interest to geologists on Earth as it forms different minerals at different pressures, thereby serving as a proxy for how deep within the Earth's mantle rocks originated at. In the lower atmosphere of HD 189733b it could have far stranger properties, since it sublimates (turns directly from a solid to gas) at about 1300 K (depending on pressure). Thus it could evaporate within the lower atmosphere, rise till it met a temperature inversion, where the temperature fell below the sublimation point, then fall as snow till the temperature rose high enough to sublimate it again.

Wednesday 22 February 2012

A Permian forest preserved in volcanic ash.

Plants are an important part of all terrestrial ecosystems on Earth, and are abundant in the fossil record, but the relationship between plants in ancient environments is often unclear, since most plant fossils represent disarticulated specimens, removed from their life positions. Fossil forests are well documented in many parts of the world, and some give excellent records of the trees that formed them, but most of these show poor preservation, and are made up of either trunks or stumps without evidence of the rest of the plants.

In a paper published in the Proceedings of the National Academy of Sciences on 21 February 2012, a team of scientists lead by Jun Wang of the State Key Laboratory of Palaeobiology and Stratigraphy at Nanjing Institute of Geology and Palaeontology describe the preservation of an area of Early Permian forest, roughly 298 million years old, preserved largely intact by volcanic ash fall; what the researchers refer to as a vegetational Pompeii. The site covers over 1000 m² in the Wuda Coal Field in Inner Mongolia.

An artists impression of part of the Wuda Forest. The tall, slim trees on the right are Sigillaria, which is related to modern Club Mosses. The taller trees on the left are Cordaites, an early form of Conifer. The lower story comprises Marattialean Tree Ferns and Noeggerathiales, a spore bearing plant of uncertain affinities. The vine is a form of Sphenopteris, a seed fern (plants with foliage resembling ferns that produced seeds; not actually closely related to ferns). There is a herbaceous layer, mostly of the fern Nemejcopteris fermaeformis, and Sphenophyllum, a relative of modern Horsetails. From Wang et al. (2012).

The Wuda Forrest was made up of several distinct layers of vegetation, as with modern forests.

The tallest trees were the Lycopsid Sigillaria and the primitive conifer Cordaites, both of which could reach heights of 25 m. These seem to have occurred as individual trees standing above the canopy, rather than as a true layer of the forest.

Leaves of Sigillaria. Scale bar 1 cm. From Wang et al. (2012) Supplementary material.

Stem/trunk of Sigillaria. Scale bar 2 cm. From Wang et al. (2012) Supplementary material.

Strobilius (soft cone) of Sigillaria. Scale bar 2 cm. From Wang et al. (2012) Supplementary material.

Leaves of Cordaites. Scale bar 2 cm. From Wang et al. (2012) Supplementary material.

Reproductive structure of Cordaites. Scale bar 2 cm. From Wang et al. (2012) Supplementary material.

The main tree canopy was at a height of 10-15 m, and was made up largely of Marattialean Tree Ferns, with some early Cycads and Noeggerathiales, early vascular plants of uncertain affinities. A vine of the genus Sphenopteris grew in this canopy. This was a seed fern, a plant with leaves resembling a fern, but which produced seeds, and which was not closely related to ferns.

Leaves (a & c) and (b & d) sporangia of Pecopteris, a Marattialean Tree Fern. Scale bar 2 mm in (a & c), 500 μm in (b & d). From Wang et al. (2012) Supplementary material.

Leaves of Pecopteris, a Marattialean Tree Fern. Scale bar 2 cm. From Wang et al. (2012) Supplementary material.

Leaves of Pecopteris, a Marattialean Tree Fern. Scale bar 2 cm. From Wang et al. (2012) Supplementary material.

Leaves of Pecopteris, a Marattialean Tree Fern. Scale bar 2 cm. From Wang et al. (2012) Supplementary material.

Leaves of Pecopteris, a Marattialean Tree Fern. Scale bar 3 cm. From Wang et al. (2012) Supplementary material.

Noeggerathiales. (a-d) Tingia unita: (a) a crown with strobili and once pinnate compound leaves attached to the stem, (b) isolated strobilus, (c) leaf with only large pinnules exposed, and (d) leaf with both large and small pinnules exposed; (e-h) Paratingia wudensis: (e) a crown with strobili and once pinnate compound leaves attached to the stem, (f) leaf with only large pinnules exposed, and (g) with small pinnules exposed after degagement, (h) a number of leaves likely attached to a common stem; (i and j) Paratingia sp.: (i) a crown with strobili and once pinnate compound leaves attached to the stem, (j) a leaf with both large and small pinnules visible. (Scale bars, 3 cm in a and h; 1 cm b–d; 2 cm e–j.) From Wang et al. (2012) Supplementary material.

Seeds of the Cycad Samaropsis. Scale bar 2 cm. From Wang et al. (2012) Supplementary material.

The vine Sigillaria. Scale bar 2 cm. From Wang et al. (2012) Supplementary material.

Finally there was a herbaceous ground cover layer, made up of the fern Nemejcopteris fermaeformis, and the Sphenopsids Sphenophyllum and Asterophyllites.

The Sphenopsid (Horsetail) Asterophyllites. Scale bar 2 cm. From Wang et al. (2012) Supplementary material.

At the time when the Wuda Forest was growing it would have been located on the Northwest of the North China Block, a small continental landmass in the tropical Paleotethys Ocean, unattached to any other land. The flora of Wuda, and other East Asian Permian plant assemblages, resemble, but are not identical too, the flora of Europe and North America, and are distinct from Gondwanan floras of the same period. Carboniferous forests, which are better studied and understood than Permian forests, are not thought to have the distinct floral layering seen in Wuda (and indeed modern forests) suggesting this was a Permian development.

An artists impression of part of the Wuda Forest, at the far end to the top illustration. From Wang et al. (2012).